The reduction scheme is a means-tested benefit to help people on low incomes.

Leader of Bristol's Liberal Democrat Group Gary Hopkins said: "We believe there's a severe danger the way he's done that is illegal and could lead to a terrible mess in Bristol if a legal challenge comes in and the whole thing collapses."

'Immoral'

He added he had written to the mayor outlining his concerns and how another council, Haringey, attempted the same approach but was blocked from doing so after a judicial review.

Carla Denyer from the Green party described the proposed cuts as "immoral".

She added: "They would inevitably see visits from bailiffs imposed on the poorest in Bristol, as those already under immense pressure due to cost of living increases are simply unable to pay.